(1) Field of the Invention
The present invention relates to an electro-mechanical brake system and an electro-mechanical brake apparatus used for the electro-mechanical brake system, and more particularly to an electro-mechanical brake system preferably employed for a system provided with a parking brake function and an electro-mechanical brake apparatus used for the electro-mechanical brake system.
(2) Description of the Related Art
Conventionally, as a control method of specifying a normal brake line system in the case that a brake line system gets out of order, and carries over a brake control by one brake line system, in an electro-mechanical brake system having two brake line systems, there has been known a method described in patent document 1 (JP-A-2001-206209). In this example, in the case that an ascent of a braking pressure is not detected at a time of a pressure intensifying control in an electronic control brake system having two brake line systems combined and connected to one pressure regulating portion, each of the brake line systems is coupled to the pressure regulating portion one by one, and it is detected whether or not the braking pressure of the coupled brake line system is ascended. Accordingly, it is determined that the brake line system in which the ascent of the braking pressure is confirmed is normal, and the brake control is carried over only by the normal brake line system. In accordance with this method, even in the case that any malfunction is generated in the brake line system, it is possible to control the brake on the basis of the electronic control in place of a braking operation by a human power, and it is possible to avoid a deterioration of an operability and a deterioration of a safety.
However, in the structure described in JP-A-2001-206209, there is not disclosed a safety in the case that that the parking brake gets out of order. In general, in the case that the parking brake gets out of order, the parking brake can be substituted by setting a transmission to a low speed gear in a vehicle having a manual transmission or setting a transmission to a parking range in a vehicle having an automatic transmission. However, (1) in the case that a malfunction of the parking brake is identified by outputting a parking brake actuation instruction in a state in which a driver cancels a regular brake, or (2) in the case that the malfunction of the parking brake is identified after outputting the parking brake actuation instruction and canceling the regular brake in a state in which the driver applies the regular brake, there is a possibility that a stop state of the vehicle is not maintained and a danger is generated.
Further, in an electro-mechanical parking brake apparatus in which a braking member is actuated by a power generated by a motor, a braking force is generated by a friction force generated between the braking member and a braked member, and a stop state of a vehicle is held by a pad pressing force holding means, a parking brake actuation state is generated after a parking brake actuation switch is operated and an operation of the pressing force holding means and an operation check thereof are finished. Accordingly, a time required until the parking brake actuation state is generated after the parking brake actuation switch is operated becomes longer than a wire type parking brake apparatus. Therefore, there is a possibility that a probability at which the states in the items (1) and (2) are generated becomes higher, and a brake control at a time when the malfunction of the parking brake is generated is necessary.